Casting Out Cast Iron

You may have noticed us repairing water lines at all hours of the day lately.  A great many of our lines installed in the 1970’s and 1980’s have been breaking as the ground shrinks and swells with vacillating temperatures.  These repairs have cost us a great deal of time, money, and sleep.

So what’s going on?  Most of the problematic lines have been constructed of ordinary cast iron, which is an alloy of iron, carbon, and some other trace elements.  As you can see from the image below, the carbon in cast iron takes the form of tiny little threads.  These little threads can lead to cracks when the iron is stressed, as when the earth shifts around a water pipe.

So that’s why our older water lines are having a rough winter.  We’re doing the next generation a favor by replacing them with a different material.  Instead of ordinary cast iron, we’re using a material known as “ductile iron.”  Invented in 1943, ductile iron includes magnesium in the recipe, causing the carbon to form spheres, rather than those problematic threads.  The result is a more durable material which can better withstand the forces of nature.

Understand, that there is still a lot of of cast iron pipe in Bridgewater, so there will be more breakages to come.  But check back around 2040, and our water system will be ready for anything winter can shell out.

A microscopic view of cast iron, on the left, and ductile iron.

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